TY - JOUR
T1 - Retinoblastoma-related protein pRb2/p130 and suppression of tumor growth in vivo
AU - Howard, Candace M.
AU - Claudio, Pier Paolo
AU - Gallia, Gary L.
AU - Gordon, Jennifer
AU - Giordano, Giovan Giacomo
AU - Hauck, Walter W.
AU - Khalili, Kamel
AU - Giordano, Antonio
PY - 1998/10/7
Y1 - 1998/10/7
N2 - The RB/p105 and p107 genes of the retinoblastoma family are tumor suppressor genes whose proteins are inactivated by interaction with T- antigen proteins encoded by polyomaviruses (e.g., simian virus 40 and human JC virus), which have been found to be highly tumorigenic in animals. A variety of indirect evidence suggests that another member of the retinoblastoma gene family, RB2/p130, is also a tumor suppressor gene. To investigate the putative tumor suppressor activity of RB2/p130 more directly, we utilized a tetracycline-regulated gene expression system to control expression of the encoded protein pRb2/p130 in JC virus-induced hamster brain tumor cells and to study the effects of pRb2/p130 on the growth of such tumor cells in nude mice. The ability of pRb2/p130 to interact with JC virus T antigen was also studied. Methods: Northern blot hybridization analyses were performed on samples of total cellular RNA to measure RB2/p130 and β-actin messenger RNA levels. Immunoprecipitation and western blot analyses were used to determine T-antigen and pRb2/p130 protein levels and to assess the phosphorylation status of these proteins. Tumor cells were injected subcutaneously into nude mice, and tumor growth, with or without induced expression of pRb2/p130, was monitored. Results: Induction of pRb2/p130 expression brought about a 3.2-fold, or 69% (95% confidence interval = 64%- 73%), reduction in final tumor mass in nude mice. We also demonstrated that JC virus T antigen binds hypophosphorylated pRb2/p130 and that stimulation of pRb2/p130 expression overcomes cellular transformation mediated by this antigen. Conclusion: Our findings support the hypothesis that RB2/p130 is a tumor suppressor gene.
AB - The RB/p105 and p107 genes of the retinoblastoma family are tumor suppressor genes whose proteins are inactivated by interaction with T- antigen proteins encoded by polyomaviruses (e.g., simian virus 40 and human JC virus), which have been found to be highly tumorigenic in animals. A variety of indirect evidence suggests that another member of the retinoblastoma gene family, RB2/p130, is also a tumor suppressor gene. To investigate the putative tumor suppressor activity of RB2/p130 more directly, we utilized a tetracycline-regulated gene expression system to control expression of the encoded protein pRb2/p130 in JC virus-induced hamster brain tumor cells and to study the effects of pRb2/p130 on the growth of such tumor cells in nude mice. The ability of pRb2/p130 to interact with JC virus T antigen was also studied. Methods: Northern blot hybridization analyses were performed on samples of total cellular RNA to measure RB2/p130 and β-actin messenger RNA levels. Immunoprecipitation and western blot analyses were used to determine T-antigen and pRb2/p130 protein levels and to assess the phosphorylation status of these proteins. Tumor cells were injected subcutaneously into nude mice, and tumor growth, with or without induced expression of pRb2/p130, was monitored. Results: Induction of pRb2/p130 expression brought about a 3.2-fold, or 69% (95% confidence interval = 64%- 73%), reduction in final tumor mass in nude mice. We also demonstrated that JC virus T antigen binds hypophosphorylated pRb2/p130 and that stimulation of pRb2/p130 expression overcomes cellular transformation mediated by this antigen. Conclusion: Our findings support the hypothesis that RB2/p130 is a tumor suppressor gene.
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U2 - 10.1093/jnci/90.19.1451
DO - 10.1093/jnci/90.19.1451
M3 - Article
C2 - 9776410
AN - SCOPUS:0032494460
SN - 0027-8874
VL - 90
SP - 1451
EP - 1460
JO - Journal of the National Cancer Institute
JF - Journal of the National Cancer Institute
IS - 19
ER -